System and method for promoting inter-ply slippage

ABSTRACT

A composite part forming system for shaping a composite material blank having a plurality of plies, the composite part forming system comprising opposing tools including shape-forming features, an actuator, and a composite tensioning system. The composite tensioning system is connectable to a periphery of the composite material blank to apply tension to the composite material blank the first and second tools are moved together to cause the composite material blank to conform to the shape-forming features. The composite tensioning system is configured to apply more tension to wrinkle prone plies of the composite material blank than to non-wrinkle prone plies as the composite material blank is caused to conform to the shape-forming features.

RELATED APPLICATIONS

The present non-provisional patent application is related to and claimspriority benefit of prior-filed US provisional patent application SerialApplication No. 63/138,609, filed Jan. 18, 2021, titled SYSTEM ANDMETHOD FOR PROMOTING INTER-PLY SLIPPAGE. The above-referenced USprovisional patent application is hereby incorporated by reference intothe present patent application in its entirety.

BACKGROUND

Stamp forming is often used for rapid manufacturing of thermoplasticcomposite laminates, and drape forming is often used to rapidly layupthermosetting composites. In both applications, as part thicknessincreases, bend radius decreases, or angle of bending increases, thecomposites become prone to wrinkling on concave sides and bridging onconvex sides of the formed part. Such wrinkling and bridging areconsidered rejectable conditions for aerospace parts.

Wrinkling is reduced by tensioning a part blank with springs orretainers attached via holes in manufacturing excess of the part blank.For example, knotted wire or clevis type clips pull on the entirethickness of the part blank. This reduces the ability of the part blankto “book” at the edge of the laminate. Booking is necessary to avoidwrinkling or bridging in bend regions due to the differing path lengthsthrough the thickness after forming.

Complex, multi-piece tooling with side action can be used to minimizewrinkling and bridging by incorporating moving tool segments tostrategically time laminate compaction. For example, pressure may beapplied in a sequence that promotes inter-ply slippage while keepingmolten material in tension to avoid wrinkling. This can be expensive,may require more maintenance than simple two-piece tooling, and mayrequire extensive experience to design and operate properly.

SUMMARY

Embodiments of the invention solve the above-mentioned problems andother problems and provide a distinct advancement in the art ofcomposite part forming systems. More particularly, the inventionprovides a composite part forming system that promotes inter-plyslippage between plies of a composite material blank.

An embodiment of the composite part forming system broadly comprises afemale tool, an actuator, a male tool, and composite material tensioningsystem. The composite material tensioning system induces more tension tosome of the plies depending on whether those plies are wrinkle prone ornot.

The female tool includes concave radiused inner corners and convexradiused lead corners. The female tool is formed of a substantiallyrigid material configured for supporting composite material during layupand prior to and/or during curing.

The actuator is configured to urge the male tool and female tooltogether. In one embodiment, the actuator supports or suspends the maletool above the female tool and actuates the male tool downward towardthe female tool.

The male tool includes convex radiused inner corners and concaveradiused lead corners. The male tool is formed of substantially rigidmaterial configured for shaping the composite material during layup andprior to and/or during curing.

The tensioning system comprises opposing first and second clevises andopposing first and second clevis pins. The tensioning system may alsoinclude biasing members (e.g., springs), cables, linkages, or similarcomponents for applying tension in the composite material.

The first clevis is U-shaped or C-shaped and includes opposing holes forreceiving the first clevis pin therethrough. The opposing holes looselyalign with a tension hole in excess manufacturing portions of thecomposite material. The opposing holes are offset from each other in thedirection of applied tension so that the first clevis pin is oriented ata non-perpendicular angle in the tension hole relative to the plies.

The first clevis pin is configured to be inserted through the opposingholes and tension hole to link the first clevis to the compositematerial. The first clevis pin is also configured to be orienteddiagonally through the tension hole due to the offset positioning of theopposing holes.

The second clevis is U-shaped or C-shaped and includes opposing holesfor receiving the second clevis pin therethrough. The opposing holesalign with another tension hole in excess manufacturing portions of thecomposite material opposite the tension hole. Unlike the opposing holesof the first clevis, the opposing holes of the second clevis may beaxially aligned so that the second clevis pin is perpendicular to thedirection of applied tension. Alternatively, the opposing holes of thesecond clevis may be offset from each other similar to the opposingholes of the first clevis.

The second clevis pin may be substantially similar to the first clevispin. The second clevis pin is configured to extend through the opposingholes of the second clevis and the tension hole of the compositematerial.

In use, the clevises are positioned at certain locations along theperiphery of the composite material with the opposing holes of theclevises aligned with the tension holes of the composite material. Theclevis pins are inserted into the opposing holes of the clevises andthrough the tension holes of the composite material.

The clevises are then pulled in opposite directions from each other toinduce tension in plies of the composite material via the clevis pins.The clevis pins induce more tension to some of the plies depending onwhether those plies are wrinkle prone or not (based on their position inthe completed part). In this case, the upper plies are more susceptibleto wrinkling due to their closer proximity to the male tool and thus areengaged with more tension by the diagonally oriented clevis than thelower plies.

The male tool is then moved by the actuator toward the female tool untilthe male tool and female tool are fully engaged with each other. Thecomposite material complies with shape-forming features of the male tooland female tool so that the composite material takes a desired shapewhen the male tool and female tool are fully engaged with each other.The clevis pins may pull through the composite material when tensionexceeds bearing strength of the composite material.

The above-described composite part forming system provides severaladvantages. For example, plies of the composite material that are on theinside of a bend (and thus are more susceptible to wrinkling) arestretched under more tension than plies in the middle or on the outsideof the bend. This difference in tension endured by adjacent pliespromotes inter-ply slippage, which prevents wrinkling and bridging.

The composite part forming system can be used in aircraft production,automobile production, and other applications that use thermoplasticcomposite stamp forming, thermosetting laminate hot drape forming, andthe like. The composite part forming system also reduces scrap.

Another embodiment is a composite tensioning system broadly comprising aclevis and clevis pin in which the clevis is U-shaped or C-shaped andincludes opposing holes that are aligned with each other for receivingthe clevis pin perpendicularly therethrough.

The clevis pin is configured to extend perpendicularly through thealigned opposing holes and a tension hole of composite material. Thetension hole is tapered on its outer side. That is, outer edges of thetension hole are initially closer to the clevis pin in plies that aremore susceptible to wrinkling and farther away in plies that are lesssusceptible to wrinkling. To that end, the tension hole may be machinedto a desired shape.

In use, the clevis pin induces more tension to some of the pliesdepending on whether those plies are wrinkle prone or not (based ontheir position in the completed part). In this case, the upper plies aremore susceptible to wrinkling due to their closer proximity to the maletool and thus are engaged with more tension by the clevis pin than thelower plies according to the tapered outer sides of the tension holes.This difference in tension endured by adjacent plies promotes inter-plyslippage, which prevents wrinkling and bridging.

Another embodiment is a composite tensioning system broadly comprising aclevis and clevis pin in which the clevis is U-shaped or C-shaped andincludes opposing holes that have different dimensions to accommodatethe clevis pin. For example, one hole may have a relatively largerdiameter while the opposing hole may have a relatively smaller diameter.

The clevis pin includes a number of step-down ledges and is configuredto be inserted perpendicularly through the opposing holes of the clevisand a tension hole of composite material. The clevis pin thus forms adiscrete tapered profile.

The clevis pin induces more tension to some plies of composite materialdepending on whether those plies are wrinkle prone or not (based ontheir position in the completed part). In this case, the upper plies aremore susceptible to wrinkling due to their proximity to the male tooland thus are engaged with more tension by more prominent step-downledges of the clevis pin. The lower plies are less susceptible towrinkling and thus are engaged with less tension by the less prominentstep-down ledges of the clevis pin. This difference in tension enduredby adjacent plies promotes inter-ply slippage, which prevents wrinklingand bridging. The benefit is further enhanced by the larger engagementarea with the higher tension plies since the larger area can providemore tension before the soft surrounding laminate deforms.

Another embodiment is a composite tensioning system broadly comprisingand clevis pin in which the clevis is U-shaped or C-shaped and includesa single hole on side of the clevis. The clevis pin is configured toextend cantilever through the hole of the clevis and at least partiallythrough a tension hole of composite material. The clevis pin does notextend fully through the tension hole when fully inserted.

In use, the clevis pin engages only some plies of composite material. Inthis way, the clevis pin induces more tension to some of the pliesdepending on whether those plies are wrinkle prone or not (based ontheir position in the completed part). In this case, the upper plies aremore susceptible to wrinkling due to their proximity to the male tooland thus are engaged directly by the clevis pin. The lower plies areonly indirectly under tension via the directly-engaged plies. Thisdifference in tension endured by adjacent plies promotes inter-plyslippage, which prevents wrinkling and bridging.

Another embodiment is a composite tensioning system broadly comprising acantilever pin including a neck and a head. The cantilever pin isconfigured to be attached to a wire on a distal end of the cantileverpin opposite the head.

The neck is configured to extend through a tension hole of compositematerial. The head is wider than the neck and is configured to anchorthe cantilever pin in the tension hole or prevent the cantilever pinfrom being pulled through the tension hole.

In use, the wire pulls the cantilever pin via the distal end of thecantilever pin. The cantilever load induces more tension in some of theplies of composite material depending on whether those plies are wrinkleprone or not (based on their position in the completed part). To thatend, the cantilever pin may rotate about a midplane. In this case, theupper plies are more susceptible to wrinkling due to their proximity tothe male tool and are engaged with more tension by the distal end of thecantilever pin. The lower plies are less susceptible to wrinkling andthus are engaged with less tension by the cantilever pin or may bepushed into forming process. This difference in tension endured byadjacent plies promotes inter-ply slippage, which prevents wrinkling andbridging.

Another embodiment is a hot drape forming system broadly comprising amold, an inflatable bladder, an actuator, and a composite tensioningsystem. The composite tensioning system may be substantially similar toone of the composite tensioning systems described previously.

The mold includes convex radiused inner corners and concave radiusedlead corners. The mold is formed of substantially rigid materialconfigured for shaping the composite material.

The inflatable bladder is positioned above the composite materialopposite the mold and is flexible, malleable, or compliant to shape thecomposite material around the mold when the inflatable bladder isinflated or actuated (after being inflated) against the mold. Theinflatable bladder may have a biasing shape to assist in pressing thecomposite material along sides of the mold.

The actuator is positioned above the inflatable bladder and isconfigured to move the inflatable bladder into engagement with thecomposite material. The actuator may be further configured to compressthe inflatable bladder against the mold so the inflatable bladder shapesthe composite material around the mold.

The composite tensioning system includes a biasing element, tensionwires, and tension connectors (clevises and clevis pins or cantileverpins as described above). The composite tensioning system is configuredto induce tension in the composite material as the composite material isdraped over the mold via the inflatable bladder.

The biasing elements is configured to exert a tension force on thetension wires and may include springs, weights, pressurized or vacuumsystems, or the like. The composite tensioning system is configured tomove along the axis of movement of the inflatable bladder (e.g.,downward) during forming to more effectively control an amount oftension on the composite material.

The tension wires connect the biasing elements to the composite materialvia the tension connectors for transferring the tension force from thebiasing elements to the composite material. The tension wires areconfigured to at least partially wrap around the inflatable bladder asthe inflatable bladder presses down the sides of the mold.

The tension connectors (clevises and clevis pins or cantilever pins asdescribed above) connect the tension wires to the composite material.The tension connectors are configured to distribute tension to each plyin the composite material according to the ply's susceptibility towrinkling.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. Other aspectsand advantages of the present invention will be apparent from thefollowing detailed description of the embodiments and the accompanyingdrawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Embodiments of the present invention are described in detail below withreference to the attached drawing figures, wherein:

FIG. 1 is an elevation view of a composite part forming systemconstructed in accordance with an embodiment of the invention;

FIG. 2 is another elevation view of the composite part forming system ofFIG. 1;

FIG. 3 is an elevation view of a composite part formed by the compositepart forming system of FIG. 1;

FIG. 4 is an enlarged elevation view of certain components of thecomposite part forming system of FIG. 1;

FIG. 5 is an enlarged elevation view of certain components of acomposite part forming system constructed in accordance with anotherembodiment of the invention;

FIG. 6 is an enlarged elevation view of certain components of acomposite part forming system constructed in accordance with anotherembodiment of the invention;

FIG. 7 is an enlarged elevation view of certain components of acomposite part forming system constructed in accordance with anotherembodiment of the invention;

FIG. 8 is an enlarged elevation view of certain components of acomposite part forming system constructed in accordance with anotherembodiment of the invention;

FIG. 9 is an elevation view of a composite part forming systemconstructed in accordance with another embodiment of the invention; and

FIG. 10 is another elevation view of the composite part forming systemof FIG. 9.

The drawing figures do not limit the present invention to the specificembodiments disclosed and described herein. The drawings are notnecessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following detailed description of the invention references theaccompanying drawings that illustrate specific embodiments in which theinvention can be practiced. The embodiments are intended to describeaspects of the invention in sufficient detail to enable those skilled inthe art to practice the invention. Other embodiments can be utilized andchanges can be made without departing from the scope of the presentinvention. The following detailed description is, therefore, not to betaken in a limiting sense. The scope of the present invention is definedonly by the appended claims, along with the full scope of equivalents towhich such claims are entitled.

Turning to FIGS. 1-4, a composite part forming system 10 constructed inaccordance with an embodiment of the invention is illustrated. Thecomposite part forming system 10 broadly comprises a female tool 12, anactuator 14, a male tool 16, and composite material tensioning system18.

The female tool 12 may be a mold, layup tool, bladder, or the like andmay have concave radiused inner corners 20 and convex radiused leadcorners 22. The female tool 16 may be made of a substantially rigidmaterial configured for supporting a composite material blank (e.g.,composite material 100) during layup and prior to and/or during curing.

The actuator 14 may be configured to urge the male tool 16 and femaletool 12 together. In one embodiment, the actuator 14 supports orsuspends the male tool 16 above the female tool 12 and actuates the maletool 16 downward toward the female tool 12.

The male tool 16 may be a mold, layup tool, bladder, or the like and mayhave convex radiused inner corners 24 and concave radiused lead corners26. The male tool 16 may be made of a substantially rigid materialconfigured for shaping the composite material 100 during layup and priorto and/or during curing.

The composite material tensioning system 18 broadly comprises opposingfirst and second clevises 28A, B, and opposing first and second clevispins 30A, B. Two clevises and two clevis pins are shown, but any numberof clevises and clevis pins may be used to apply tension in thecomposite material 100. The composite material tensioning system 18 mayalso include biasing members, cables, linkages, or similar componentsfor applying tension in the composite material 100.

The first clevis 28A is U-shaped or C-shaped and includes opposing holes32A,B for receiving the first clevis pin 30A therethrough. The opposingholes 32A,B loosely align with a tension hole 102 in excessmanufacturing portions of the composite material 100. The opposing holes32A,B may be offset from each other in the direction of applied tensionso that the first clevis pin 30A is angled in the tension hole 102.

The first clevis pin 30A is configured to be inserted through theopposing holes 32A,B and tension hole 102 to link the first clevis 28Ato the composite material 100. The first clevis pin 30A may be straightand configured to be oriented diagonally through the tension hole 102due to the offset positioning of the opposing holes 32A,B.Alternatively, the first clevis pin 30A may have an angled, bent,eccentric, tapered, or diagonal shape. The first clevis pin 30A may alsoinclude a head or flange for preventing the first clevis pin 30A fromcompletely passing through the first clevis 28A and tension hole 102.The first clevis pin 30A may be configured to be secured to thecomposite material 100 via linchpin or similar component.

The second clevis 28B is U-shaped or C-shaped and includes opposingholes 34A,B for receiving the second clevis pin 30B therethrough. Theopposing holes 32 align with another tension hole in excessmanufacturing portions of the composite material 100 opposite thetension hole 102. Unlike the opposing holes 32A,B, the opposing holes34A,B may be axially aligned so that the second clevis pin 30B isperpendicular to the direction of applied tension. Alternatively, theopposing holes 34A,B may be offset from each other similar to theopposing holes 32A,B.

The second clevis pin 30B may be substantially similar the first clevispin 30A. The second clevis pin 30B may be configured to extend throughthe opposing holes 34A,B of the second clevis 28B and the tension hole102 of the composite material 100. The second clevis pin 30B may bestraight or may have an angled, bent, eccentric, or tapered, or diagonalshape.

In use, the clevises 28A,B are positioned at certain locations along theperiphery of the composite material 100 with the opposing holes of theclevises 28A,B aligned with the tension holes of the composite material100. The clevis pins 30A,B are inserted into the opposing holes 32A, Band 34A, B of the clevises 28A, B and through the tension holes of thecomposite material 100. To that end, the tension holes may be drilled ormachined into the composite material 100.

The clevises 28A,B may then be pulled in opposite directions from eachother to induce tension in plies 104 of the composite material 100 viathe clevis pins 30A,B. Various tensioning arrangements are possible forapplying force to each of the clevises 28A,B to pull them in oppositedirections. One example of a tensioning arrangement having biasingelements for pulling the clevises in opposite directions is describedbelow in connection with FIG. 5. As another example, a lever may be usedto produce shear in the periphery outside of the composite part toenforce the displacement to promote laminate booking. Importantly, thediagonally oriented clevis pin 30A induce more tension to some of theplies depending on whether those plies are wrinkle prone or not (basedon their position in the completed part). In the illustrated example,the upper plies are more susceptible to wrinkling and thus are engagedwith more tension by the diagonally oriented clevis 28A than the lowerplies.

Ply tension may be a function of a ply's position in the compositematerial 100. For example, a non-curved, diagonal clevis pin may applylinearly decreasing tension from one side of the composite material 100to the opposing side of the composite material 100. Alternatively, plytension may increase by larger orders or may increase by a taperedamount.

The male tool 16 may then be moved by the actuator 14 toward the femaletool 12 until the male tool 16 and female tool 12 are fully engaged witheach other. The composite material 100 complies with shape-formingfeatures of the male tool 16 and female tool 12 so that the compositematerial 100 takes a desired shape when the male tool 16 and female tool12 are fully engaged with each other. The clevis pins 30A, B may pullthrough the composite material when tension exceeds bearing strength ofthe composite material.

The above-described composite part forming system 10 provides severaladvantages. For example, plies of the composite material 100 that are onthe inside of a bend (and thus are more susceptible to wrinkling) arestretched under more tension than plies in the middle or on the outsideof the bend. This difference in tension endured by adjacent pliespromotes inter-ply slippage, which prevents wrinkling and bridging.

The composite part forming system 10 can be used in aircraft production,automobile production, and other applications that use thermoplasticcomposite stamp forming, thermosetting laminate hot drape forming, andthe like. The composite part forming system 10 also reduces scrap andtooling costs.

Turning to FIG. 5, a clevis 200 and clevis pin 202 constructed inaccordance with another embodiment is illustrated. The clevis 200 may beU-shaped or C-shaped and includes opposing holes 204 that are alignedwith each other.

The clevis pin 202 may be configured to extend perpendicularly throughthe aligned opposing holes 204 and a tension hole 302 of compositematerial 300. The tension hole 302 may be tapered on its outer side.That is, outer edges of the tension hole 302 are initially closer to theclevis pin 202 in plies that are more susceptible to wrinkling andfarther away in plies that are less susceptible to wrinkling. To thatend, the tension hole 302 may be machined to a desired shape.

In use, the clevis pin 202 may induce more tension to some of the plies304 depending on whether those plies are wrinkle prone or not (based ontheir position in the completed part). In the illustrated example, theupper plies are more susceptible to wrinkling and thus are engaged withmore tension by the clevis pin 202 than the lower plies due to thetapered outer sides of the tension holes 302. This difference in tensionendured by adjacent plies promotes inter-ply slippage, which preventswrinkling and bridging.

Turning to FIG. 6, a clevis 400 and clevis pin 402 constructed inaccordance with another embodiment is illustrated. The clevis 400 may beU-shaped or C-shaped and includes opposing holes 404. The opposing holes404 may have different dimensions to accommodate the clevis pin 402. Forexample, one hole may have a relatively larger diameter while theopposing hole may have a relatively smaller diameter.

The clevis pin 402 may include a plurality of step-down ledges 406 andmay be configured to be inserted perpendicularly through the opposingholes 404 of the clevis 400 and a tension hole 502 of composite material500. The clevis pin 402 thus may form a discrete tapered profile.

The clevis pin 402 may induce more tension to some of plies 504 ofcomposite material 500 depending on whether those plies are wrinkleprone or not (based on their position in the completed part). In theillustrated example, the upper plies are more susceptible to wrinklingand thus are engaged with more tension by more prominent ones of thestep-down ledges 406 of the clevis pin 402. The lower plies are lesssusceptible to wrinkling and thus are engaged with less tension by theless prominent ones of the step-down ledges 406 of the clevis pin 402.This difference in tension endured by adjacent plies promotes inter-plyslippage, which prevents wrinkling and bridging.

Turning to FIG. 7, a clevis 600 and clevis pin 602 constructed inaccordance with another embodiment is illustrated. The clevis 600 may beU-shaped or C-shaped and may include a single hole 604.

The clevis pin 602 is configured to extend cantilever through the hole604 of the clevis 600 and at least partially through a tension hole 702of composite material 700. The clevis pin 602 does not extend fullythrough the tension hole 702 when fully inserted.

In use, the clevis pin 602 may engage only some plies 704 of thecomposite material 700. In this way, the clevis pin 602 may induce moretension to some of the plies depending on whether those plies arewrinkle prone or not (based on their position in the completed part). Inthe illustrated example, the upper plies are more susceptible towrinkling and thus are engaged directly by the clevis pin 602. The lowerplies are only indirectly under tension via the directly-engaged plies.This difference in tension endured by adjacent plies promotes inter-plyslippage, which prevents wrinkling and bridging.

Turning to another embodiment of the invention illustrated in FIG. 8,one or both of the tensioning connectors of a tensioning system maycomprise a cantilever pin 800 employed without the clevises used in theprior embodiments. Each cantilever pin 800 may include a neck 802 and ahead 804. Each cantilever pin 800 may be attached to a wire 806 on adistal end 808 opposite the head 804.

The neck 802 may be configured to extend through a tension hole 902 ofcomposite material 900. The head 804 may be wider than the neck 802 andmay anchor the cantilever pin 800 in the tension hole 902 or prevent thecantilever pin 800 from being pulled through the tension hole 902.

In use, the wire 806 pulls the cantilever pin 800 via the distal end 808of the cantilever pin 800. The cantilever load may induce more tensionin some of the plies 904 of composite material 900 depending on whetherthose plies are wrinkle prone or not (based on their position in thecompleted part). To that end, the cantilever pin 800 may rotate about amidplane. In the illustrated example, the upper plies are moresusceptible to wrinkling and are engaged with more tension by the distalend 808 of the cantilever pin 800. The lower plies are less susceptibleto wrinkling and thus are engaged with less tension by the cantileverpin 800 or may be pushed into forming process. This difference intension endured by adjacent plies promotes inter-ply slippage, whichprevents wrinkling and bridging.

Turning to FIGS. 9 and 10, a hot drape forming system 1000 constructedin accordance with another embodiment is illustrated. The hot drapeforming system 1000 broadly comprises a mold 1002, an inflatable bladder1004, an actuator 1006, and a composite tensioning system 1008. Thecomposite tensioning system 1008 may be substantially similar to thecomposite material tensioning system 18 described previously, and maylikewise include clevises as described in connection with FIGS. 1-4 or asystem using a cantilever pin without a clevis, as described inconnection with FIG. 5.

The mold 1002 may be a male layup tool, bladder, or the like and mayhave convex radiused inner corners 1010 and concave radiused leadcorners 1012. The mold 1002 may be made of a substantially rigidmaterial configured for shaping the composite material 2000.

The inflatable bladder 1004 may be positioned above the compositematerial 2000 opposite the mold 1002 and may be flexible, malleable, orcompliant to shape the composite material 2000 around the mold 1002 whenthe inflatable bladder 1004 is inflated. The inflatable bladder 1004 mayhave a biasing shape to assist in pressing the composite material 2000along sides of the mold 1002.

The actuator 1006 may be positioned above the inflatable bladder 1004and may be configured to move the inflatable bladder 1004 intoengagement with the composite material 2000. The actuator 1006 may befurther configured to compress the inflatable bladder 1004 against themold 1002 so the inflatable bladder 1004 shapes the composite material2000 around the mold 1002.

The composite tensioning system 1008 may include a biasing element 1014,optional tension wires, and tension connectors 1016 (clevises and clevispins or cantilever pins as described above). The composite tensioningsystem 1008 may be configured to induce tension in the compositematerial 2000 as the composite material 2000 is draped over the mold1002 via the inflatable bladder 1004.

The biasing elements 1014 may be configured to exert a tension force onthe tension connectors 1016 via the tension wires and may includesprings, weights, pressurized or vacuum systems, or the like. Thecomposite tensioning system 1008 may be configured to move along theaxis of movement of the inflatable bladder (e.g., downward) duringforming to more effectively control an amount of tension on thecomposite material 2000.

The tension wires may connect the biasing elements 1014 to the compositematerial 2000 via the tension connectors 1016 for transferring thetension force from the biasing elements 1014 to the composite material2000. The tension wires may be configured to at least partially wraparound the inflatable bladder 1004 as the inflatable bladder 1004presses down the sides of the mold 1002.

The tension connectors 1016 (clevises and clevis pins or cantilever pinsas described above) may connect the tension wires to the compositematerial 2000. The tension connectors are configured to distributetension to each ply in the composite material 2000 according to theply's susceptibility to wrinkling.

In use, the composite material 2000 may be connected to the tensionwires via the tension connectors 1016. Initial tension may be applied tothe tension wires to suspend the composite material 2000 above the mold1002. This may reduce the need for heating the mold 1002 since coolingof the composite material 2000 can be delayed via the suspension. Theinitial tension may also assist in blank trellising in certain areas ofthe composite material 2000.

The inflatable bladder 1004 may then be inflated. Alternatively, theinflatable bladder 1004 may be pre-inflated or permanently inflated. Theactuator 1006 may also press the inflatable bladder 1004 against thecomposite material 2000.

The biasing elements 1014 may induce additional tension into thecomposite material 2000 so that the composite material 2000 is subjectedto a forming tension. Furthermore, the biasing elements 1014 and tensionwires may be moved to change the origin of the tension force, therebyaffecting the direction, intensity, and timing of the tension.

To promote early tensioning in the forming process, the tension wiresmay be pulled from a position that causes the inflatable bladder 1004 toquickly contact the tension wires. To promote late tensioning, thetension wires may be pulled from a position where the inflatable bladder1004 does not contact the tension wires until later in the formingprocess or not at all.

The tension connectors 1016 (clevises and clevis pins or cantilever pinsas described above) may induce more tension to some of the pliesdepending on whether those plies are wrinkle prone or not (based ontheir position in the completed part). In the illustrated example, thelower plies are more susceptible to wrinkling near the convex radiusedinner corners 1010 and thus are engaged with more tension than the upperplies. This difference in tension endured by adjacent plies promotesinter-ply slippage, which prevents wrinkling and bridging. The tensionconnectors 1016 may pull through the composite material 2000 whentension exceeds bearing strength of the composite material 2000, as seenin FIG. 10.

Although the invention has been described with reference to theembodiments illustrated in the attached drawing figures, it is notedthat equivalents may be employed and substitutions made herein withoutdeparting from the scope of the invention as recited in the claims.

Having thus described various embodiments of the invention, what isclaimed as new and desired to be protected by Letters Patent includesthe following:
 1. A composite part forming system for shaping acomposite material blank having a plurality of plies, the composite partforming system comprising: a first tool including shape-formingfeatures; and a composite tensioning system connectable to a peripheryof the composite material blank to apply tension to the compositematerial blank such that the composite tensioning system applies moretension to wrinkle prone plies of the composite material blank than tonon-wrinkle prone plies of the composite material blank as the compositematerial blank is caused to conform to the shape-forming features of thefirst tool.
 2. The composite part forming system of claim 1, furthercomprising a second tool complementary to the first tool.
 3. Thecomposite part forming system of claim 1, wherein the compositetensioning system further comprises: a plurality of clevises includingclevis pin holes, the plurality of clevises being configured to bepositioned near tension openings in the composite material blank; and aplurality of clevis pins configured to be inserted through the clevispin holes of the plurality of clevises and the tension openings of thecomposite material blank to connect the clevises to the compositematerial blank, the plurality of clevises being configured to be pulledto induce tension in the composite material blank, the plurality ofclevis pins being configured to induce more tension to wrinkle proneplies of the composite material blank than to non-wrinkle prone plieswhen the composite material blank conforms to the shape-forming featuresof the first tool.
 4. The composite part forming system of claim 1, theplurality of clevis pins being oriented diagonally relative to theplurality of clevis pins and the composite material blank.
 5. Thecomposite part forming system of claim 1, the plurality of clevis pinsincluding step-down ledges.
 6. The composite part forming system ofclaim 1, wherein the composite tensioning system further comprises: aplurality of clevises each including a clevis pin hole, the plurality ofclevises being configured to be positioned near tension openings in thecomposite material blank; and a plurality of cantilever clevis pinsconfigured to be inserted through the clevis pin holes of the pluralityof clevises and partially through the tension openings of the compositematerial blank to connect the clevises to the composite material blank,the plurality of clevises being configured to be pulled to inducetension in the composite material blank, the plurality of clevis pinsbeing configured to induce more tension to wrinkle prone plies of thecomposite material blank than to non-wrinkle prone plies when thecomposite material blank conforms to the shape-forming features of thefirst tool.
 7. The composite part forming system of claim 1, wherein thecomposite tensioning system comprises a plurality of tension wiresconnected to the clevises and a biasing element for inducing the tensionin the composite material blank via the plurality of tension wires. 8.The composite part forming system of claim 1, wherein the compositetensioning system is movable to control the tension.
 9. The compositepart forming system of claim 2, wherein: the first tool comprises a maletool, and the second tool comprises an inflatable bladder; and theinflatable bladder causes the composite material blank to conform to theshape-forming features when the inflatable bladder is actuated over themale tool.
 10. The composite part forming system of claim 9, wherein thecomposite tensioning system is configured to initially suspend thecomposite material blank over the male tool to delay cooling of thecomposite material blank.
 11. The composite part forming system of claim1, further comprising: a plurality of cantilever pins each including: aneck configured to be inserted through the tension holes of thecomposite material blank, and a head configured to retain the neck inthe tension holes of the composite material blank, the plurality ofcantilever pins being configured to induce more tension to wrinkle proneplies of the composite material blank than to non-wrinkle prone plieswhen the male tool and female tools shape the composite material blank.12. A method of forming a composite material part, the method comprisingsteps of: connecting a composite tensioning system to a periphery of acomposite material blank; placing the composite material blank between afirst tool and a complementary, at least one of the first and secondtool including shape-forming features; moving the first tool toward thecomplementary second tool; and applying tension to the compositematerial blank via the composite tensioning system so that the compositetensioning system applies more tension to wrinkle prone plies of thecomposite material blank than to non-wrinkle prone plies of thecomposite material blank as the composite material blank is caused toconform to the shape-forming features.
 13. The method of claim 12, theconnecting step including inserting a clevis pin through clevis pinholes of a clevis of the composite tensioning system and through atension opening of the composite material blank so that the clevis pinis oriented at a non-perpendicular angle to plies of the compositematerial blank.
 14. The method of claim 12, the connecting stepincluding inserting a clevis pin through clevis pin holes of a clevis ofthe composite tensioning system and through a tension opening of thecomposite material blank, the clevis pin including step-down ledges. 15.The method of claim 12, the connecting step including inserting acantilever clevis pin through a clevis pin hole of a clevis of thecomposite tensioning system and partially through a tension opening ofthe composite material blank.
 16. The method of claim 12, the applyingtension step including pulling the composite material blank via abiasing element.
 17. The method of claim 12, further comprising a stepof moving the composite tensioning system to control the tension. 18.The method of claim 12, wherein the first tool comprises an inflatablebladder and the second tool comprises a male tool, the method furthercomprising a step of inflating the inflatable bladder.
 19. The method ofclaim 18, further comprising a step of suspending the composite materialblank over the male tool to delay cooling of the composite materialblank.
 20. A hot drape forming system for shaping a composite materialblank having a plurality of plies, the hot drape forming systemcomprising: a male tool including shape-forming features; an inflatablebladder suspended above the male tool; an actuator configured to movethe inflatable bladder toward the male tool; and a composite tensioningsystem comprising: a plurality of tension connectors connectable to aperiphery of the composite material blank to apply tension to thecomposite material blank as the inflatable bladder is moved toward themale tool to cause the composite material blank to conform to theshape-forming features of the at least one of the first and secondtools; a biasing element configured to induce the tension in thecomposite material blank; and a plurality of wires linking the pluralityof tension connectors to the biasing element, the composite tensioningsystem being configured to apply more tension to wrinkle prone plies ofthe composite material blank than to non-wrinkle prone plies as thecomposite material blank is caused to conform to the shape-formingfeatures.